This invention serves a purpose in the joint fields of exercise systems combined with game playing. This invention adds to the game and exercise functions the use of a radio link, accelerometers, and radio antennas. This invention measures motions of a remote body. This invention is also useful in fields which need to determine remote body motion in a simple manner.
It is desirable to be able to measure motion of a remote body, using the simplest possible configuration of transducers and radio transmitters. This need arises in systems which aid exercise. Motion of a body can be detected with accelerometers. The accelerometer data is reported to a computer, by wire or radio, and calculations are performed to obtain velocity and position values.
A troublesome error, which this invention overcomes, arises when the accelerometers tilt away from their normal horizontal or vertical positions. The tilt comes from rotational motion of the body, usually rotation of the human body in the vertical plane. The force of gravity makes tilt look like motion, and therefore the tilt is a form of noise, or unwanted data.
This error has caused accelerometers not to be used in some applications, and has caused use of other more complicated motion reporting systems. One of these other systems is to place brightly marked coverings, or leggings and sleeving, on the moving body, and tracking the motion with optical systems, such as a video camera. An equivalent system places bright jewels or reflective elements on the body. These optical systems have the disadvantage of requiring special unnatural attachments. They also have trouble functioning well in bright ambient light, or in lighting conditions where undesired bright reflections occur.
Another system for reporting body motion is to place on all joints of the moving body angular position sensors, and to report the readings of the angular sensors to a computer system.
Applications for such motion detection include: sports movement study, from golf to tennis to baseball (batter swing) to football (blocking) and to running and pole vaulting. Another application is study of moving bodies so that games and animation displaying human and animal bodies can be made to look highly realistic, and to minimize stiffness often seen in animation.
Electronic games are popular and interest is growing. The operator sits before a screen, and uses a hand controller, and sometimes also a foot and head controller, to steer and operate while watching the screen. There is no whole body exercise. This invention adds to the value of games by providing concurrent exercise, and adds to the value of exercise by incorporating the entertainment of game play.
The present inventions describes a method and system for reporting body motion, accurately, without need for painted and brightly colored bodies, and without need for angle sensing devices attached to the various points, and independent of ambient lighting effects and variations. The present invention uses accelerometers and adds a correction for the tilt of the body.
The invention is also valuable, in general, for measuring tilt, or angular orientation, of a remote device, regardless of distance, without accelerometers.
One of the concepts in physics of both Newton and Einstein is that both acceleration and gravity produce the same indistinguishable effect on a mass. Acceleration is changing motion, which mass resists, the resistance being a force, with the relationship described by the basic formula F=MA. F is the force, M is the mass, and A is the acceleration. Yet a force equal to and indistinguishable from acceleration can also be produced by no motion at all, by simply residing in a gravitational field. An observer within the mass, having only scales to measure force, cannot tell which of the actions, one with substantial motion, the other with none, is producing the force. No experimenter has found a way to allow the observer to tell which of the two sources produces the force, nor find a difference in the two forces. This phenomenon explains in part why accelerometers mounted to a body free to move, and residing in a gravitation field, are unable to tell from their readings, whether the body is moving, or is merely tilting within a gravitational field. Some other means of sensing must be brought into play, namely something to measure tilt within the gravity field, as described in this invention.
The prior art includes several patents, some by the present inventor. This invention evolves from the first patent listed below. Other patents follow.
1. U.S. Pat. No. 5,989,157: Exercising System With Inertial Game Playing. This patent provides for a person to both exercise and to play games. Exercising is made more fun and less boring, and game playing is made more worthwhile by working full body stimulation and acquisition of body physical skills. There is a need to add to electronic game entertainment the larger benefits of whole body exercise, or conversely, to add to large muscle exercise the fun of electronic game entertainment. This patent describes a game playing exerciser.
2. U.S. Pat. No. 4,782,342: Proximity Identification System With Lateral Flux Paths, by Charles Walton, covers rod to coil and rod-to-rod radio coupling, which are used in a different way in this current invention.
3. U.S. Pat. No. 4,888,474: Proximity Identification System With Lateral Flux Magnetic Rod Coupling. Shows further variations of the rod to rod and loop to loop antennas utilized in this current invention.
4. U.S. Pat. No. 4,925,189: Body Mounted Video Game Device, by Thomas F. Brauenig. Inertially operated switches are mounted on the users body and control a game display on the screen. Inertially operated switches are simple on-off devices and do not have the linear infinitely variable quality of accelerometers, and also these switches cannot distinguish between actuation caused by acceleration and action caused by tilt or angular deviation. That is, a switch can be made to close by rapid movement, or a switch can be made to close by sufficient tilt and letting gravity cause the action. Means for distinguishing the two effects is a primary portion of this current invention.
5. U.S. Pat. No. 5,645,513 Exercising Apparatus which Interacts with a Video Game Apparatus During Exercise. For feedback from the user, this invention uses either interrupted light beams or body mounted switches. It lacks the smoother infinitely variable more sophisticated control possible with analog devices such as accelerometers. It will respond to position indicators but not to velocity or acceleration values. Large shifts in body position are not possible.
6. For reading accelerometers mounted on a mobile body, and with display responsive to motion of the body, there is published prior art, which includes an article in Poptronics magazine, May 2000, pages 49-54, titled: xe2x80x9cRobotics, Tilt Sensorsxe2x80x9d, enclosed. This technical article describes sensing tilt by accelerometers, but not motion itself, or any other function.
7. At health clubs, several types of electronic interaction between machine and user have been tried. Walking or stride machines report pace and distance covered. Heart beat rate is measured and sensed several ways. A voice report with audible heart beat and audible muscle effects adds interest. There is little or no game playing.
8. Other competing art uses rigid angle sensing devices clamped to the limbs of a user to sense and report angular position of various limbs relative to one another, or there are specially color coded bars on the limbs to visually record angular positions.
A primary use of the invention is to improve systems which combine exercise with game playing. The invention makes practical the use of accelerometers on the human body to report body motion and control displays on a viewing screen. There is a short range radio link from the body to the base station.
The invention corrects for errors induced by gravity upon the accelerometers. The invention uses the signals received at a base station from transmitting antennas on a remote body, to determine the tilt angle and to measure the acceleration of the body.
Knowledge of the angular position of the body allows correction for the effects of gravity upon accelerometers attached to the body. The angular knowledge is obtained by measuring the polarization quality of signals from loop and rod antennas.
The receiving station, or base station, carries multiple antennas which selectively respond to the polarized waves. The receiving antennas are typically at right angles to one another. The signal strength, or reading, from the receiving antennas is digitized, that is, converted to a digital value, by analog to digital converters, and are thus put into digital form accepted by the computer. From the relative signal strengths received the angular orientation, also referred to as tilt angle, of the transmitting antennas is determined.
From the tilt angle, corrections for gravity effects in two or more dimensions are applied to the accelerometer values, and then integration is applied to obtain the position value. The calculated position is typically displayed on a television or computer type monitor.
A secondary object of the present invention is to aid a person desiring to stay in good health through exercise, by combining the requirement for vigorous motion with the mental stimulation associated with playing electronic games.
The moving device may be an object, or the instruments may be mounted on a human body. Other uses are for studying dance movements, or athletic competition movements, or for controlling unmanned intelligent transport vehicles, or for reporting positions of portions of machinery. In some applications the angular orientation of remote bodies is of interest even with out accelerometer readings.
The preferred form of modulation of the polarized radio signal is pulse width modulation, where the width of the pulse represents the magnitude of the accelerometer transducer reading, or other transducers. An alternative form of modulation is to digitize the transducer values and to send data by digital pulse modulation.